1. Field of the Invention
The present invention relates to an image capture apparatus and a control method therefor, and in particular, relates to an image capture apparatus for performing automatic focus detection based on contrast evaluation values and a method for controlling the image capture apparatus.
2. Description of the Related Art
An image capture apparatus is known in which a specific subject, such as a person's face, is focused on by performing automatic focus detection based on contrast evaluation values for focus detection areas that include the specific subject among a plurality of focus detection areas that are each located at a fixed position and each has a fixed size (Japanese Patent Laid-Open No. 2010-39200).
Bringing the focus to a subject is, however, not always easy when the automatic focus detection based on contrast evaluation values is applied to focus detection areas that are each located at a fixed position and each has a fixed size, unlike cases in which the positions and sizes of focus detection areas are set in accordance with a detected subject region. This is because when a single focus detection area includes a plurality of subjects that are located at very different distances, a conflict will arise between contrast evaluation values of far and near subjects.
In particular, the possibility of not being able to perform proper focus detection increases when each focus detection area includes only a small portion of a subject that is intended to be focused on. Such a situation can arise, for example, when the face of a person who is at a much closer distance than the background is intended to be focused on and automatic focus detection based on contrast evaluation values (contrast AF) is performed on a focus detection area that includes only a small portion of a face region.
In order to mitigate this problem, Japanese Patent Laid-Open No. 2010-39200 discloses a technique in which priorities are assigned to focus detection areas, and a focus detection area to be ultimately focused on is selected according to the focus detection results for focus detection areas having high priority. This technique, however, requires sorting according to priority, and also requires a longer time for focus detection because, irrespective of priority, focus detection is performed on all focus detection areas that include the face.
The focus detection based on contrast evaluation values (contrast AF) in principle has a difficulty in bringing the focus to a low-contrast subject. Thus, not the contrast on the center portion of a person's face but the contrast at the contour of the face is likely to be captured when focus detection is performed on a focus detection area that includes only a portion of the face. This may result in failing to detect the focus (failing to detect an in-focus distance) in the center portion of the face, such as the eyes and the mouth, and being able to detect the focus only in focus detection areas that include portions forming the contour of the face, such as the ears.
Incidentally, an in-focus display is known in which a frame-shaped indicator is superimposed on an EVF image in order to explicitly inform the user of focus detection areas in which the focus can be detected. In the case of the above-described example, however, there could possibly be a situation in which indicators for focus detection areas that correspond to the contour portion of the face are displayed because their focuses can be detected, but indicators for focus detection areas that correspond to the center portion of the face are not displayed because their focuses cannot be detected.
In this case, there is a problem in that it is difficult to discriminate whether or not the face is focused on because no indicates are displayed for the focus detection areas corresponding to the center portion of the face. In particular, such a situation that the focus is detected in only the contour portion is likely to occur when the face portion is underexposed and the background is bright, as in a backlight scene or when the face portion is overexposed due to direct sunlight.